Invasive Species Management

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Fall Stewardship

Fall Stewardship Webinar Series

Jeffco ISM and CSU Extension (Boulder, Jeffco, and Larimer Counties) are hosting a 4-week speaker series from Sept 15 through Oct. 6.

Join us for talks that will educate and inform landowners on land stewardship for small acreages and the latest trends. The talks are geared for owners of 10 acres or more but all are welcome.

Free – Register at

Sessions will be held virtually from 6:00–7:30 pm 

September 15

Dryland Pasture Management - Joe Brummer, CSU Dept. of Soil and Crop Sciences

September 22 

Fall Noxious Weed Management - Joe Swanson, Boulder County Parks and Open Space

September 29

Living With Wildlife - Mary Ann Bonnell, Jefferson County Open Space

Protecting Your Livestock - Sharon Bokan, Boulder County CSU Extension

October 6

Forest Stewardship - Nate Beckman, CSFS Golden District

Need Noxious Weed Advice?

We are not able to provide site visits in 2021 but are monitoring calls and questions. See our contact information on the right-hand side of this page.

What We Do

Orange hawkweed flowerhead.The Jefferson County Invasive Species Management program provides the public with information and offers solutions for managing invasive species and supports good stewardship of the land.  

We ensure the compliance with Colorado’s noxious weed, forest pest, and agricultural vertebrate pest regulations on private, county, and state lands.  We also provide technical assistance and support to county departments who are responsible for managing county owned lands.

The program coordinates with private, local, state, and federal agencies to achieve regional pest control.

Who We Are

Canada thistle flower.Our staff includes the Invasive Species Management Coordinator and limited summer help.

Weed of the Month

Each month we will feature a noxious weed to help landowners identify weeds they may encounter on their property.

Yellow toadflax 

September 2021

Yellow toadflax

Linaria vulgaris

Yellow toadflax, sometimes called butter-and-eggs, is a member of the Plantaginaceae family (formerly Scrophulariaceae).  This perennial spreads by seed and extensive spreading underground roots.  Large colonies can be found in disturbed areas, meadows, pastures, and rights-of-way.  It is often one of the first plants to return after a forest fire.

The yellow flowers are snapdragon-shaped with a distinctive long spur and often have an orange throat.   The flowers grow in groups at the end of the stems and can be found from June through September.  

Multiple stems grow from the crown.  Plants can grow to two feet tall.  Leaves are narrow, waxy and attach directly to the stems.  Each plant can produce 15,000 to 30,000 seeds that will last for about 10 years in the soil.

The taxonomy of Linaria species can be challenging because there is a lot of hybridization in the field, especially Yellow toadflax and Dalmatian toadflax here in Colorado.  Yellow toadflax is native to Britain, Europe, and Asia.  In the US, it is an escaped ornamental and has been grown here since the late 1600s.  It has also been used for its herbal properties and as a source for dye.


Flora of North America

Invasive Plant Atlas

National Invasive Species Information Center  

Weed Control in Natural Areas in the Western United States

Wisconsin Horticulture Division of Extension

LG_NoxWeed_2020_cover Opens in new window

A Landowner's Guide - Developing a Noxious Weed Management Plan

We developed this guide to assist landowners.  The information provides steps to develop a management plan for properties that have noxious weeds.

Download your copy

yellow_flag_iris Weed Spotter

The Weed Spotter program is a citizen science based effort to detect 6 high priority species on Jeffco Open Space parks.  Learn more at our Citizen Science page.

Myrtle spurge flower.Invasive Species 101 Webinar Series

A four session speaker series to inform landowners on invasive species terminology, identification, treatment, and the  latest trends.